The Washington critic., 1887-11-10
THE CONGRESSIONAL LIBRARY.
The Great Care with which tho Foun
dations Are Being Laid.

lhE CUNGRESSlUNAL LlbhAhl.
The Great Care with which tho Foun-
dations Are Being Laid.
The Congressional Library site as yet
gives no other indication OF the mag.
ntlcent building which is to be erected
there than large hole In the ground
and the sheds which have been erected
on First street east to protect the
cement from dampness. The cxcava.
tions for the foundations have about
been finished. Under the masonry
foundations is to be a foundation six
feet deep composed Of concrete. A
trench for this has been dug about one.
eighth Of the way around, commencing
on the east side and extending around
the southeast corner, and Is now wait
ing TO be flled with the concrete.
This is delayed by the non arrival OF
acceptable cement. The first install.
ment-2 900 barrels-and the second
400 barrels-were rejected, as they did
not meet the required tests Of strength.
These tests ore very exhaustive. A
sample is taken from every fifty barrels
as It arrives to the basement OF au old
building on Second street. Here It Is
mixed with the proper quantity Of
water and the plastic mass placed Ia
moulds which form 1t into blocks one
inch thick, three inches long and
shaped somewhat like figure s. The
area at the narrowest part, where the
block was broken in yesterday, being
one square inch.
These blocks are placed In a machine,
which, holding the two ends firmly.
pulls them apart, at the same time
| registering the number of pounds
necessary TO pull the block In two.
All cement used Is required to resist
tensile strain of 800 pounds to the
square inch. A number OF blocks are
made from each sample Of cement. One
Of these is tested twenty four hours
after 1t Is made; another Is put into
water and left submerged one week,
and then tested. This shows the
strength OF the cement under differen,
| circumstances. Good cement improves
with age. sometimes getting almost as
hard as granite. all the cement for
the new Library building is tested five
times-twice on two different machines
under Architect Smithmeyer; once each
at the Navy. Yard, District Chemist
Richardson's office, and by Colonel
| Lydecker. Another installment of 1000
barrels has just arrived, and is being
| tested.
TESTS FOR THE CEMENT.
The ground on which the concrete
foundation is laid is required TO stand
pressure of two and half tons to the
square foot, and Mr.. Smithmeyer is to
day going over the bottoms of the
trenches already dug, to see II they
are firm enough. In making these
tests four short Iron pillars are placed
on the ground about four feet apart.
These are each exactly one foot square
on the bottom. Resting on these
are two iron rails, shaped some
what like ordinary railway rails,
only instead Of being four
inches high, they are about foot in
height, and about six or eight feet long.
On these rails Is small Hat car, and
thirty tons of piglead are piled on this
car, this weight being divided equally
between the four square feet covered
by the iron pillars. This leaves large
margin Of safety over the required test
of 23 tons.
TEsTING THE SAND.
All the sand used In the building
will also be tested. This Is done by
placing 1t In glass tube, with scale
marked on one side. A certain quantity
Of the sand is placed in the tube, the
quantity, as shown by the scale, notes
aquantity of water, also shown by the
same scale, added. and the whole, after
vigorous shaking up Is allowed to
stand until the sediment has settled aud
the water becomes clear. The coarse
particles of sand or gravel settle at the
bottom of the tube, with the finer ones
on top and the fine sediment, or mud,
on top of these.
The scale shows the quantity and
proportions of each. An excess OF mud
causes the sand to be rejected.
MINING THE CONCRETE.
The plant for mixing and laying the
concrete is very complete, and proba.
bly, there is not better one anywhere.
1t is on the First street side, and COM
prlses steam crusher of the most I'm
proved pattern, which will break 200
tons OF stone per day into any sized
| pieces that may be wanted. The sand,
cement and broken stone In the
proper proportions are placed in
The steam tinker. " This is
an iron box about four feet square, aud
having a door through which the
charge is put in and removed. The
box is supported In the air by heavy
timbers, and after being filed with the
various ingredients Of concrete 1t is
whirled around for awhile by steam
and then emptied Into dump car, i"
which runs in under the machine on a
portable railroad track. These cars